KPIs differ depends on the level of volleyball
At international level the KPIs could be something like:
Serve: ratio of aces/errors about 1/2 for male and 2/3 for female
Pass: average 2.5-2.6 for male and 2.2-2.3 for female
Attack: for male left/right side 30%-35% and 20%-25% for female. For middles 40%-45% for male and 30%-35% for female
Block: 1.5 block/set for male middles and 0.8 block/set for female middles
Defense: team stats of 2-3 digs per set for male and 4-5 digs per set for female.
For lower levels, attacking KPIs could be lower but defensive KPIs could be higher.